From 0ddd10ffd2dc8c703da210b15eb6a13e84eebaae Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Wed, 3 Sep 2014 15:50:08 +0200
Subject: [PATCH 2/2] spice: make sure we don't overflow ssd->buf

Related spice-only bug.  We have a fixed 16 MB buffer here, being
presented to the spice-server as qxl video memory in case spice is
used with a non-qxl card.  It's also used with qxl in vga mode.

When using display resolutions requiring more than 16 MB of memory we
are going to overflow that buffer.  In theory the guest can write,
indirectly via spice-server.  The spice-server clears the memory after
setting a new video mode though, triggering a segfault in the overflow
case, so qemu crashes before the guest has a chance to do something
evil.

Fix that by switching to dynamic allocation for the buffer.

CVE-2014-3615

Cc: qemu-stable@nongnu.org
Cc: secalert@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
(cherry-picked from commit ab9509cceabef28071e41bdfa073083859c949a7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 ui/spice-display.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/ui/spice-display.c b/ui/spice-display.c
index 5418eb3..888346b 100644
--- a/ui/spice-display.c
+++ b/ui/spice-display.c
@@ -243,9 +243,21 @@ void qemu_spice_create_host_memslot(SimpleSpiceDisplay *ssd)
 void qemu_spice_create_host_primary(SimpleSpiceDisplay *ssd)
 {
     QXLDevSurfaceCreate surface;
+    uint64_t surface_size;
+
+    surface_size = (uint64_t) ds_get_width(ssd->ds) *
+        ds_get_height(ssd->ds) * 4;
+    assert(surface_size > 0);
+    assert(surface_size < INT_MAX);
+    if (ssd->bufsize < surface_size) {
+        ssd->bufsize = surface_size;
+        g_free(ssd->buf);
+        ssd->buf = g_malloc(ssd->bufsize);
+    }
 
-    dprint(1, "%s: %dx%d\n", __FUNCTION__,
-           ds_get_width(ssd->ds), ds_get_height(ssd->ds));
+    dprint(1, "%s: %dx%d (size %" PRIu64 "/%d)\n", __FUNCTION__,
+           ds_get_width(ssd->ds), ds_get_height(ssd->ds),
+           surface_size, ssd->bufsize);
 
     surface.format     = SPICE_SURFACE_FMT_32_xRGB;
     surface.width      = ds_get_width(ssd->ds);
@@ -287,8 +299,6 @@ void qemu_spice_display_init_common(SimpleSpiceDisplay *ssd, DisplayState *ds)
     qemu_mutex_init(&ssd->lock);
     ssd->mouse_x = -1;
     ssd->mouse_y = -1;
-    ssd->bufsize = (16 * 1024 * 1024);
-    ssd->buf = g_malloc(ssd->bufsize);
 }
 
 /* display listener callbacks */
@@ -396,7 +406,7 @@ static void interface_get_init_info(QXLInstance *sin, QXLDevInitInfo *info)
     info->num_memslots = NUM_MEMSLOTS;
     info->num_memslots_groups = NUM_MEMSLOTS_GROUPS;
     info->internal_groupslot_id = 0;
-    info->qxl_ram_size = ssd->bufsize;
+    info->qxl_ram_size = 16 * 1024 * 1024;
     info->n_surfaces = NUM_SURFACES;
 }
 
-- 
1.7.10.4

